Bale take-off machines or bale openers are used to extract fibers or fiber tufts from pressed fiber bales. To this end, a take-off unit is moved across the fiber bales. The take-off unit is fastened on a take-off arm, the height of which is set according to the fiber bales that are present. The take-off arm, in turn, is held on a take-off tower. The take-off tower makes it possible for the take-off unit to be moved across the surface of the fiber bales. To this end, the take-off tower is arranged on a horizontal drive or a rotating frame. A horizontal drive, which is usually guided on rails, is used to move across a row of bales. If the fiber bales are arranged in a circle around the take-off tower, the take-off tower is mounted on a rotating frame. A combination of a horizontal drive and a rotating frame is present when fibers or fiber tufts are extracted from a first row of fiber bales in one direction and from a second row of fiber bales in the opposite direction.
The bale opener is located at the beginning of processing lines in a spinning preparation (blowroom) for processing fiber material, for example cotton or synthetic fibers or mixtures thereof, and has a decisive influence on the continuity of the sequences that take place within the spinning preparation. In the bale opener, the fiber material delivered in bales is extracted from the bales by taking off fiber tufts and is transferred to a pneumatic transport system. The pneumatic transport system carries the fiber tufts through pipelines to the downstream cleaning machines.
In bale openers that are common today, the take-off arm is held on the take-off tower so as to be vertically adjustable. The vertical adjustment is usually carried out by means of chain or belt drives, at which the take-off arm is raised or lowered. Sensors are provided on the take-off arm in order to determine the position of the take-off arm relative to the surface of the fiber bales.
Various embodiments of lifting mechanisms for take-off arms are known from the prior art. For example, CH 686 188 A5 discloses a take-off arm comprising a chain drive for vertical adjustment. The take-off arm is suspended on a counter-weight via a cable and deflection rollers, wherein the height of the take-off arm is adjusted by means of a lifting motor via a chain drive.
A bale opener is disclosed in CH 675 386 A, which moves the take-off arm in a circular manner over the fiber bales to be opened. In so doing, the take-off arm is moved in the vertical position thereof via four threaded rods located at the corners. The threaded rods are rotated simultaneously in order to raise or lower the take-off arm. The threaded rods are connected via a gearbox in order to ensure a synchronized movement of the threaded rods.
The disadvantage of the disclosed design according to the prior art is the complex construction of the lifting mechanisms, which either make it necessary to provide a suspension that is independent of the actual movement, or the lifting mechanisms must have a plurality of lifting drives, which move the take-off arm simultaneously. As a result, an exact orientation of the take-off arm relative to the fiber bales to be opened is complicated and, due to operation-induced wear, a readjustment must be carried out periodically. In addition, a complex sensor system is required for the positioning and control of the lifting mechanism.